Lens device, imaging apparatus, and method of detecting position of movable lens

1. A lens device comprising: a lens that is movable in an optical axis direction; a rotating member that rotates in conjunction with movement of the lens in the optical axis direction; a first signal detection section that detects a signal which changes in accordance with a position of the lens in the optical axis direction; a second signal detection section that detects a signal which changes in accordance with an amount of rotation of the rotating member; a first lens position detection section that detects the position of the lens based on the signal detected by the first signal detection section; a second lens position detection section that detects the position of the lens based on the signal detected by the second signal detection section; a control section that performs first control for outputting information of the position of the lens, which is detected by the first lens position detection section, and thereafter performs second control for outputting information of the position of the lens, which is detected by the second lens position detection section, if power is supplied; and a direction determination section that determines whether or not a direction of an optical axis of the lens device is same as a reference direction, wherein in a case where the direction determined by the direction determination section is different from the reference direction, after the rotating member rotates, the second lens position detection section sets the position of the lens, which is detected by the first lens position detection section after power is supplied, as a reference position, and detects the position of the lens by detecting an amount of displacement from the reference position based on the signal which is detected by the second signal detection section in accordance with rotation of the rotating member, and wherein in a case where the direction determined by the direction determination section is same as the reference direction, after the rotating member rotates, the second lens position detection section detects the position of the lens based on the signal which is detected by the second signal detection section.

2. The lens device according to claim 1 , wherein the first signal detection section detects two signals of which phases fluctuating in accordance with the position of the lens deviate from each other, wherein the second signal detection section includes a first magnetic recording member and a second magnetic recording member, which are fixed onto the rotating member in accordance with a rotation direction of the rotating member and in which magnetic signals respectively having different wavelengths are recorded, and a sensor section that detects a first signal, which corresponds to a magnetic signal having a first wavelength recorded in the first magnetic recording member, and a second signal, of which a phase deviates from that of the first signal, and detects a third signal, which corresponds to a magnetic signal having a second wavelength recorded in the second magnetic recording member and different from the first wavelength, and a fourth signal of which a phase deviates from that of the third signal, wherein the lens device further comprises a storage section that stores, at each of positions obtained whenever the position of the lens in the optical axis direction is changed, first angle information, which corresponds to each of the positions calculated from the signals detected by the first signal detection section, and second angle information, which corresponds to each of the positions calculated from the signal detected by the sensor section, in association with each other, and wherein the direction determination section determines that the direction of the optical axis of the lens device is different from the reference direction when a difference between the second angle information, which is stored in the storage section in association with the first angle information calculated from the signal detected by the first signal detection section, and the second angle information, which is calculated from the signal detected by the sensor section, is equal to or greater than a threshold value, and determines that the direction of the optical axis of the lens device is same as the reference direction when the difference is less than the threshold value.

3. The lens device according to claim 1 , wherein the first signal detection section includes a magnet that is fixed onto the lens, and a plurality of magnetic detection sections that are provided with intervals interposed therebetween in the optical axis direction at positions facing a region through which the magnet passes when the lens moves in the optical axis direction, and wherein until the rotating member rotates after power is supplied to the lens device, the first lens position detection section specifies a magnetic detection section, which corresponds to the position of the lens detected by the second lens position detection section, among the plurality of magnetic detection sections, based on the position, and detects the position of the lens based on a signal detected by the specified magnetic detection section.

4. The lens device according to claim 2 , wherein the first signal detection section includes a magnet that is fixed onto the lens, and a plurality of magnetic detection sections that are provided with intervals interposed therebetween in the optical axis direction at positions facing a region through which the magnet passes when the lens moves in the optical axis direction, and wherein until the rotating member rotates after power is supplied to the lens device, the first lens position detection section specifies a magnetic detection section, which corresponds to the position of the lens detected by the second lens position detection section, among the plurality of magnetic detection sections, based on the position, and detects the position of the lens based on a signal detected by the specified magnetic detection section.

5. An imaging apparatus comprising: the lens device according to claim 1 ; and an imaging element that captures an image of a subject through the lens device.

6. A method of detecting a position of a movable lens, the method comprising: a first signal detection step of detecting a signal changing in accordance with a position of a lens which is mounted on a lens device and is movable in an optical axis direction; a second signal detection step of detecting a signal changing in accordance with an amount of rotation of a rotating member which rotates in conjunction with movement of the lens in the optical axis direction; a first lens position detection step of detecting the position of the lens based on the signal detected in the first signal detection step; a second lens position detection step of detecting the position of the lens based on the signal detected in the second signal detection step; a control step of performing first control for outputting information of the position of the lens, which is detected in the first lens position detection step, and thereafter performing second control for outputting information of the position of the lens, which is detected in the second lens position detection step, after the rotating member rotates, if power is supplied to the lens device; and a direction determination step of determining whether or not a direction of an optical axis of the lens device is same as a reference direction, wherein in a case where the direction determined by the direction determination step is different from the reference direction, after the rotating member rotates, the second lens position detection step sets the position of the lens, which is detected by the first lens position detection step after power is supplied, as a reference position, and detects the position of the lens by detecting an amount of displacement from the reference position based on the signal which is detected by the second signal detection step in accordance with rotation of the rotating member, and wherein in a case where the direction determined by the direction determination step is same as the reference direction, after the rotating member rotates, the second lens position detection step detects the position of the lens based on the signal which is detected by the second signal detection step.